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This paper investigates electrical balance (EB) in hybrid junctions as a method of achieving transmitter–receiver isolation in single antenna full duplex wireless systems. A novel technique for maximizing isolation in EB duplexers is presented, and we show that the maximum achievable isolation is proportional to the variance of the antenna reflection coefficient with respect to frequency. Consequently, antenna characteristics can have a significant detrimental impact on the isolation bandwidth. Simulations that include embedded antenna measurements show a mean isolation of 62 dB over a 20-MHz bandwidth at 1.9 GHz but relatively poor performance at wider bandwidths. Furthermore, the operational environment can have a significant impact on isolation performance. We present a novel method of characterizing radio reflections being returned to a single antenna. Results show as little as 39 dB of attenuation in the radio echo for a highly reflective indoor environment at 1.9 GHz and that the mean isolation of an EB duplexer is reduced by 7 dB in this environment. A full duplex architecture exploiting EB is proposed. [ABSTRACT FROM PUBLISHER]

In this paper, we seek to characterize the performance of spatial modulation (SM) and spatial multiplexing (SMX) with an experimental testbed. Two National Instruments (NI) PXIe devices are used for the system testing: one for the transmitter and one for the receiver. The digital signal processing (DSP) that formats the information data in preparation for transmission is described, along with the DSP that recovers the information data. In addition, the hardware limitations of the system are also analyzed. The average bit-error ratio (ABER) of the system is validated through both theoretical analysis and simulation results for SM and SMX under the line-of-sight (LoS) channel conditions. [ABSTRACT FROM PUBLISHER]

The electromagnetic coupling of antennas with the human body is a well-known, but often neglected, problem in body area network (BAN) communications. The resulting distortion of the antenna's free-space characteristics may, in turn, demand more complex terminals to cope with the different conditions encountered as antennas are mounted on different parts of the body and/or varying separations from the skin. Therefore, in this paper, we propose a mounting method to provide a more stable response and to reduce the antenna's coupling to the body for ultra-wideband (UWB) BAN applications. The proposed mounting method is evaluated on two UWB BAN antennas, characterizing the antennas coupling with the body by analyzing variations in the antennas reflection coefficient between 4–9 GHz, when mounted at different distances from the skin and at different locations on the body. The modified mounting method was found to increase the correlation coefficient between the antenna's reflection coefficient when in free space and mounted using 5 mm of spacer, for the two antennas, from 0.22 and 0.13, to 0.66 and 0.90. The free-space characteristics of the modified antennas are also tested, showing a reduction of up to 4.7 dB of radiated power into the body. [ABSTRACT FROM AUTHOR]

Code orthogonality is a useful indicator in determining the performance of the synchronous downlink of third-generation Universal Mobile Telecommunication System (UMTS) Terrestrial Radio Access systems. In this paper, previous work on quantifying code orthogonality for single-antenna [or single-input single-output (SISO)] links is extended to fixed beamforming and transmit diversity schemes. Code orthogonality estimates from real measured channel data are extracted for typical outdoor radio environments. The results indicate that the spatial conditioning of fixed beamforming radio channels generally improves code orthogonality. In contrast, full code-rate transmit diversity schemes degrade code orthogonality. [ABSTRACT FROM AUTHOR]

Within Mobile VCE, a team of several leading U.K. universities, in close association with major manufacturers and international telecom operators from the mobile industry, have been addressing the challenging task of designing transceiver structures for beyond 3G networks. Innovative approaches led to a plethora of cross- layer optimized technologies of low complexity and high robustness, allowing for the much promised multimedia-centric services over future wireless networks. This article presents a comprehensive overview of the research conducted within Mobile VCE's Core Wireless Access Research Programme, a key focus of which has naturally been on MIMO transceivers. The series of articles offers a coherent view of how the work was structured and comprises a compilation of material that has been presented in detail elsewhere (see references within the article). In this article, the first of four, MIMO channel measurements, analysis, and modeling are presented, which were then utilized to develop com- pact and distributed antenna arrays. Parallel activities led to research into low-complexity MIMO single-user space-time coding techniques, as well as SISO and MIMO multi-user CDMA-based transceivers for B3G systems. As well as feeding into the industry's in-house research program, significant extensions of this work are now in hand, within Mobile VCE's own core activity, aimed at securing major improvements in delivery efficiency in future wireless systems through cross-layer operation. [ABSTRACT FROM AUTHOR]

Channel estimation and tracking pose real problems in broadband single-carrier wireless communication systems employing multiple transmit and receive antennas. An alternative to estimating the channel is to adaptively equalize the received symbols. Several adaptive equalization solutions have been researched for systems operating in the time domain. However, these solutions tend to be computationally intensive. A low-complexity alternative is to adaptively equalize the received message in the frequency domain. In this paper, we present an adaptive frequency-domain equalization (FDE) algorithm for implementation in single-carrier (SC) multiple-input multiple-output (MIMO) systems. Furthermore, we outline a novel method of reducing the overhead required to train the proposed equalizer. Finally, we address the issues of complexity and training sequence design. Other computationally efficient adaptive FDE algorithms for use in SC systems employing single transmit and receive antennas, receive diversity, or space-lime block codes (STBC) can be found in the literature. However, the algorithm detailed in this paper can be implemented in STBC systems as well as in broadband spatial multiplexing systems, making it suitable for use in high data rate MIMO applications. [ABSTRACT FROM AUTHOR]

This article reviews wireless enabling technologies to support interworking of heterogeneous networks, and covers two relevant topics; personal area networks and multistandard terminals. The variability of the PAN channel is demonstrated, and the implications for air interface design are discussed. To ensure effective operation in shared spectrum, radio resource management and medium access control strategies for PANs are also discussed. It is recognized that terminal cost has significant implications for user acceptance; therefore, by combining functionality from different standards (cellular, wireless LAN, broadcast), cost can be reduced. Technologies and architectures relevant for multistalidard terminals are reviewed, including synchronization and linear RF processing. Finally, the potential for further simplifications within the framework of multicarrier CDMA is considered. [ABSTRACT FROM AUTHOR]

Smart antennas are widely recognized as an enabling technology for addressing the demand of future wireless network capacity when employed in place of traditional fixed-coverage sector antennas. Furthermore, switched-beam antenna systems offer a robust implementation against multipath propagation effects and reduced complexity that is inherent with fully adaptive implementations. This paper introduces a simple closed-form expression for evaluating the capacity increase of W-CDMA cellular networks employing switched-beam antennas. The expression incorporates the effect of practical antenna patterns and the impact of multipath scattering on code orthogonality, as well as that of pilot signal power. The results show that a reduction in downlink interference of approximately 6 dB can be achieved by installing an eight-beam antenna system in a 120° sector configuration when representative values of these parameters are taken into account. [ABSTRACT FROM AUTHOR]

This paper introduces a novel metric for determining the spatial decorrelation between the up- and down-link wireless bearers in frequency division duplex (FDD) networks. This metric has direct relevance to smart or adaptive antenna array base-station deployments in cellular networks, which are known to offer capacity enhancement when compared to fixed coverage solutions. In particular, the results presented were obtained from field trial measurement campaigns for both urban and rural scenarios, with the observations having a direct impact on the choice of down-link beamforming architecture in FDD applications. Further, it is shown that significant spatial decorrelation can occur in urban deployments for bearer separations as small as 5 MHz. Results are presented in terms of both instantaneous characteristics as well as time averaged estimates, thus facilitating the appraisal of smart antenna solutions in both packet and circuit switched networks. [ABSTRACT FROM AUTHOR]